Measurement of total fission gamma spectrum of 252Cf(s.f.)

The paper presents a first comprehensive measurement of the total fission gamma spectrum (TFGS) of ²⁵²Cf(s.f.) spanning an energy range from 0.2 to 14.3 MeV using stilbene scintillator spectroscopy. The measurement was performed with the ²⁵²Cf(s.f.) source placed in a flexo-rabbit ending, with a stilbene detector located at a distance of 100 cm from the source. The room effect was determined by separate measurement with a 50 cm long lead shielding cylinder placed between the source and the detector. The obtained spectrum was corrected for the effect of the ²⁵²Cf source structural parts and the flexo-rabbit ending, using correction function obtained by simulation with the MCNP6.2 code. The main benefit of this independent measurement is the wide energy range, from 0.2 up to 14.3 MeV, in a single experiment, whereas existing measurements typically cover narrower intervals. The knowledge of the TFGS is crucial for various applications involving ²⁵²Cf(s.f.) sources, including the design and analysis of nuclear systems, the validation of nuclear data, and the estimation of radiation in the nuclear medicine. The comparison of TFGS with the recently evaluated ²⁵²Cf(s.f.) prompt fission gamma spectrum (PFGS) indicates that delayed gammas may contribute above 2 MeV up to the highest energies; the current assumption was that delayed gammas contribution above 2 MeV was negligible.